Systems and methods for limited emissions refueling

ABSTRACT

A method is presented, comprising, during a first condition, including an active refueling event, receiving an indication of hydrocarbon breakthrough from the fuel vapor canister; and flowing refueling vapors into an intake manifold responsive to the indication of hydrocarbon breakthrough. Flowing refueling vapors into an intake manifold traps the vapors there until engine start-up, when the vapor can be combusted by the engine. In this way, refueling emissions may be reduced, even if the fuel vapor canister is saturated prior to, or during the refueling event.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 15/013,720 entitled “Systems and Methods forLimited Emissions Refueling,” filed on Feb. 2, 2016. The entire contentsof the above-referenced application are hereby incorporated by referencein their entirety for all purposes.

FIELD

The present description relates generally to methods and systems forrefueling a vehicle.

BACKGROUND/SUMMARY

Vehicle fuel systems include evaporative emission control systemsdesigned to reduce the release of fuel vapors to the atmosphere. Forexample, vaporized hydrocarbons (HCs) from a fuel tank may be stored ina fuel vapor canister packed with an activated carbon adsorbent whichadsorbs and stores the vapors. At a later time, when the engine is inoperation, the evaporative emission control system allows the vapors tobe purged into the engine intake manifold for use as fuel.

Adsorption of fuel vapor to activated carbon is an exothermic reaction.A hot canister thus has a lower adsorption capacity than does a coolcanister. In hot climates, and/or following a prolonged driving period,the canister temperature may become increased due to heat rejection fromthe engine, exhaust, asphalt radiation, etc. As such, the canister maybe incapable of storing enough fuel vapor to accommodate a tank fillingrefueling event without emitting hydrocarbons into atmosphere.

Other attempts to address hydrocarbon breakthrough during refuelingevents include deposing a secondary or “trap” canister downstream of theprimary fuel vapor canister in order to capture breakthroughhydrocarbons. One example approach is shown by Mani et al. in U.S. Pat.No. 9,005,352. Therein, a trap canister with a higher adsorbance thanthe main canister is selectively coupled to an outlet of the maincanister within the fuel canister vent pathway.

However, the inventors herein have recognized potential issues with suchsystems. As one example, a trap canister must significantly restrictvapor flow in order to be effective. This may lead to prolonged fueltank depressurization and may further limit the rate of refueling andthe rate of purging the canisters. If the trap canister is bypassed,hydrocarbon breakthrough may occur.

In one example, the issues described above may be addressed by a method,comprising, during a first condition, including an active refuelingevent, receiving an indication of hydrocarbon breakthrough from the fuelvapor canister; and flowing refueling vapors into an intake manifoldresponsive to the indication of hydrocarbon breakthrough. Flowingrefueling vapors into an intake manifold traps the vapors there untilengine start-up, when the vapor can be combusted by the engine. In thisway, refueling emissions may be reduced, even if the fuel vapor canisteris saturated prior to, or during the refueling event.

As one example, a hydrocarbon sensor may be placed in the canister ventpathway to detect hydrocarbon breakthrough, a canister purge valve maybe actuated to an open conformation to allow vapor flow to the engineintake. By diverting refueling vapors in this way, vehicles can obtainfuel without increasing surface hydrocarbon concentrations which maythus limit ground ozone levels on hot days.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an example vehicle propulsion system.

FIG. 2 schematically shows an example vehicle system comprising anengine system coupled to a fuel system and an evaporative emissionssystem.

FIG. 3 shows an example method for detecting and mitigating hydrocarbonemissions during a refueling event.

FIG. 4 shows a timeline for an example refueling event using the methodof FIG. 3.

FIG. 5 shows an example method for detecting and mitigating hydrocarbonemissions during a refueling event.

FIG. 6 shows a timeline for an example refueling event using the methodof FIG. 5.

DETAILED DESCRIPTION

The following description relates to systems and methods for refueling avehicle. More specifically, the description relates to system andmethods for limiting fuel vapor emissions during a refueling event. Insome jurisdictions, refueling emissions may be limited by localregulations. For example, a city or state may declare an ozone alert daywhere it is required to limit refueling in order to minimize thecreation of ground ozone via emitted hydrocarbons. As such, a vehiclemay be configured with a human-machine interface that allows a vehicleoperator to request a refueling event, and to activate or overridelimited emissions refueling parameters. An example vehicle propulsionsystem and human machine interface is depicted in FIG. 1. The vehiclemay comprise a liquid fuel tank and evaporative emissions system asdepicted in FIG. 2. During certain conditions, the capacity of the fuelvapor canister may be insufficient to store the entirety of fuel vaporgenerated when filling a fuel tank. As such, a hydrocarbon sensor may bedeposed in a canister vent pathway. If hydrocarbon breakthrough from thecanister occurs while limited emissions refueling parameters are active,the canister vent pathway may be restricted by closing a valve, such asa fuel tank isolation valve or a canister vent valve, using a methodsuch as the method shown in FIG. 3. A timeline for an example refuelingevent in accordance with the present disclosure is depicted in FIG. 4.In another example, the refueling vapors may be diverted to engineintake by opening a canister purge valve and duty-cycling a canistervent valve, using a method such as the method shown in FIG. 5. Atimeline for an example refueling event in accordance with such anadditional example of the present disclosure is depicted in FIG. 6. Insome examples, a vehicle control system may execute method of each ofthe routines of FIGS. 3 and 5, but at different operating conditions.

FIG. 1 illustrates an example vehicle propulsion system 100. Vehiclepropulsion system 100 includes a fuel burning engine 110 and a motor120. As a non-limiting example, engine 110 comprises an internalcombustion engine and motor 120 comprises an electric motor. Motor 120may be configured to utilize or consume a different energy source thanengine 110. For example, engine 110 may consume a liquid fuel (e.g.,gasoline) to produce an engine output while motor 120 may consumeelectrical energy to produce a motor output. As such, a vehicle withpropulsion system 100 may be referred to as a hybrid electric vehicle(HEV).

Vehicle propulsion system 100 may utilize a variety of differentoperational modes depending on operating conditions encountered by thevehicle propulsion system. Some of these modes may enable engine 110 tobe maintained in an off state (i.e., set to a deactivated state) wherecombustion of fuel at the engine is discontinued. For example, underselect operating conditions, motor 120 may propel the vehicle via drivewheel 130 as indicated by arrow 122 while engine 110 is deactivated.

During other operating conditions, engine 110 may be set to adeactivated state (as described above) while motor 120 may be operatedto charge energy storage device 150. For example, motor 120 may receivewheel torque from drive wheel 130 as indicated by arrow 122 where themotor may convert the kinetic energy of the vehicle to electrical energyfor storage at energy storage device 150 as indicated by arrow 124. Thisoperation may be referred to as regenerative braking of the vehicle.Thus, motor 120 can provide a generator function in some embodiments.However, in other embodiments, generator 160 may instead receive wheeltorque from drive wheel 130 (either directly, or via motor 120), wherethe generator may convert the kinetic energy of the vehicle toelectrical energy for storage at energy storage device 150 as indicatedby arrow 162.

During still other operating conditions, engine 110 may be operated bycombusting fuel received from fuel system 140 as indicated by arrow 142.For example, engine 110 may be operated to propel the vehicle via drivewheel 130 as indicated by arrow 112 while motor 120 is deactivated.During other operating conditions, both engine 110 and motor 120 mayeach be operated to propel the vehicle via drive wheel 130 as indicatedby arrows 112 and 122, respectively. A configuration where both theengine and the motor may selectively propel the vehicle may be referredto as a parallel type vehicle propulsion system. Note that in someembodiments, motor 120 may propel the vehicle via a first set of drivewheels and engine 110 may propel the vehicle via a second set of drivewheels.

In other embodiments, vehicle propulsion system 100 may be configured asa series type vehicle propulsion system, whereby the engine does notdirectly propel the drive wheels. Rather, engine 110 may be operated topower motor 120, which may in turn propel the vehicle via drive wheel130 as indicated by arrow 122. For example, during select operatingconditions, engine 110 may drive generator 160 as indicated by arrow116, which may in turn supply electrical energy to one or more of motor120 as indicated by arrow 114 or energy storage device 150 as indicatedby arrow 162. As another example, engine 110 may be operated to drivemotor 120 as indicated by arrow 125, which may in turn provide agenerator function to convert the engine output to electrical energy,where the electrical energy may be stored at energy storage device 150for later use by the motor. In some embodiments, motor 120 may beoperated to rotate engine 110, as indicated by arrow 125. Generator 160may also be operated to rotate engine 110 in addition to or as analternative to motor 120. As an example, motor 120 may be operated as astarter motor by rotating engine 110 during a cold start operation.Motor 120 and/or generator 160 may rotate engine 110 without providingfuel to the engine for combustion. For example, during an electric-onlymode of operation, rotating the engine may allow for a rotatingtransmission component to be maintained while adjusting the torqueprovided to drive wheels 130. In some scenarios, the engine may berotated unfueled to generate intake vacuum without expending fuel.

Fuel system 140 may include one or more fuel storage tanks 144 forstoring fuel on-board the vehicle. For example, fuel tank 144 may storeone or more liquid fuels, including but not limited to: gasoline,diesel, and alcohol fuels. In some examples, the fuel may be storedon-board the vehicle as a blend of two or more different fuels. Forexample, fuel tank 144 may be configured to store a blend of gasolineand ethanol (e.g., E10, E85, etc.) or a blend of gasoline and methanol(e.g., M10, M85, etc.), whereby these fuels or fuel blends may bedelivered to engine 110 as indicated by arrow 142. Still other suitablefuels or fuel blends may be supplied to engine 110, where they may becombusted at the engine to produce an engine output. The engine outputmay be utilized to propel the vehicle as indicated by arrow 112 or torecharge energy storage device 150 via motor 120 or generator 160.

In some embodiments, energy storage device 150 may be configured tostore electrical energy that may be supplied to other electrical loadsresiding on-board the vehicle (other than the motor), including cabinheating and air conditioning, engine starting, headlights, cabin audioand video systems, etc. As a non-limiting example, energy storage device150 may include one or more batteries and/or capacitors.

Control system 190 may communicate with one or more of engine 110, motor120, fuel system 140, energy storage device 150, and generator 160. Aswill be described by the process flow of FIG. 6, control system 190 mayreceive sensory feedback information from one or more of engine 110,motor 120, fuel system 140, energy storage device 150, and generator160. Further, control system 190 may send control signals to one or moreof engine 110, motor 120, fuel system 140, energy storage device 150,and generator 160 responsive to this sensory feedback. Control system190 may receive an indication of an operator requested output of thevehicle propulsion system from a vehicle operator 102. For example,control system 190 may receive sensory feedback from pedal positionsensor 193 which communicates with pedal 192. Pedal 192 may referschematically to a brake pedal and/or an accelerator pedal.

Energy storage device 150 may periodically receive electrical energyfrom a power source 180 residing external to the vehicle (e.g., not partof the vehicle) as indicated by arrow 184. As a non-limiting example,vehicle propulsion system 100 may be configured as a plug-in hybridelectric vehicle (HEV), whereby electrical energy may be supplied toenergy storage device 150 from power source 180 via an electrical energytransmission cable 182. During a recharging operation of energy storagedevice 150 from power source 180, electrical transmission cable 182 mayelectrically couple energy storage device 150 and power source 180.While the vehicle propulsion system is operated to propel the vehicle,electrical transmission cable 182 may disconnected between power source180 and energy storage device 150. Control system 190 may identifyand/or control the amount of electrical energy stored at the energystorage device, which may be referred to as the state of charge (SOC).

In other embodiments, electrical transmission cable 182 may be omitted,where electrical energy may be received wirelessly at energy storagedevice 150 from power source 180. For example, energy storage device 150may receive electrical energy from power source 180 via one or more ofelectromagnetic induction, radio waves, and electromagnetic resonance.As such, it should be appreciated that any suitable approach may be usedfor recharging energy storage device 150 from a power source that doesnot comprise part of the vehicle. In this way, motor 120 may propel thevehicle by utilizing an energy source other than the fuel utilized byengine 110.

Fuel system 140 may periodically receive fuel from a fuel sourceresiding external to the vehicle. As a non-limiting example, vehiclepropulsion system 100 may be refueled by receiving fuel via a fueldispensing device 170 as indicated by arrow 172. In some embodiments,fuel tank 144 may be configured to store the fuel received from fueldispensing device 170 until it is supplied to engine 110 for combustion.In some embodiments, control system 190 may receive an indication of thelevel of fuel stored at fuel tank 144 via a fuel level sensor. The levelof fuel stored at fuel tank 144 (e.g., as identified by the fuel levelsensor) may be communicated to the vehicle operator, for example, via afuel gauge or indication via human-machine interface 194.

Human-machine interface 194 may include a vehicle instrument panel 195.The vehicle instrument panel 195 may include indicator light(s) and/or atext-based display in which messages are displayed to an operator. Insome embodiments, the vehicle instrument panel 195 may communicate audiomessages to the operator with or without displaying a visual message.The vehicle instrument panel 195 may also include various input portionsfor receiving an operator input, such as buttons, touch screens, voiceinput/recognition, etc. For example, the vehicle instrument panel 195may include a refueling button 196 which may be manually actuated orpressed by a vehicle operator to initiate refueling. For example, asdescribed in more detail below, in response to the vehicle operatoractuating refueling button 196, a fuel tank in the vehicle may bedepressurized so that refueling may be performed. Additional interfacesfor HMI 194 including appropriate sensors and communication devices maybe located at common points surrounding the vehicle frame, such as inproximity to a vehicle trunk, engine compartment, fuel filler neck, etc.These additional interfaces may enable a controller to output messagesand/or notifications to a vehicle operator, refueling operator,mechanic, valet, etc. as well as receiving input from interfacecomponents external the primary vehicle cabin, so that an operator mayreceive from and transmit information to HMI 194 without being confinedto the vehicle cabin. In some examples, a portable computing device,such as a smartphone, laptop computer, tablet computer, etc. may be usedto interface with HMI 194, incorporating an application and interface atthe portable computing device to facilitate communication.

In some examples, vehicle instrument panel 195 may include an ECO-modeselector switch 197. ECO-mode selector switch 197 may be utilized toactivate or de-activate one or more routines, methods, and/or parametersfor vehicle operation, engine operation, fuel system operation, and/orevaporative emissions system operation. When ECO-mode is selected,reducing vehicle emissions may be prioritized with a greater weight thanduring a “normal emissions” mode of operation. For example, a vehicletraversing a border between jurisdictions with differing emissionsregulations standards may be required to activate ECO-mode upon enteringthe jurisdiction with more stringent standards. A given jurisdiction mayinvoke temporary emissions restrictions, such as an ozone alert day orsmog alert day, which require vehicles to further limit emissions. Insome embodiments, ECO-mode may be the default mode, thus requiring userinput to activate a “normal emissions” mode. In some examples, thelocation of the vehicle may be determined via an on-board GPS or othertracking service, and the current location used to automaticallydetermine whether to place the vehicle into ECO-mode. The vehicleoperator may be enabled to override ECO-mode via ECO-mode selectorswitch 197 in certain conditions, such as during an emergency. In someembodiments, an ECO-mode selector switch or other components of HMI 194may be located proximal to the fuel filler neck, allowing the vehicleoperator to override ECO-mode from a location external the vehicle. Forexample, the vehicle operator may need to add more fuel during arefueling event than would be allowed otherwise in order to preventrunning out of fuel in a sparsely populated area. As another example,peak engine efficiency may be relaxed in a scenario where the vehicleoperator is en route to a hospital. Example methods for refueling avehicle that has invoked ECO-mode are described herein and with regardto FIGS. 3 and 5.

The vehicle propulsion system 100 may also include an ambienttemperature/humidity sensor 198, and a roll stability control sensor,such as a lateral and/or longitudinal and/or yaw rate sensor(s) 199.Further, the sensor(s) 199 may include a vertical accelerometer toindicate road roughness. These devices may be connected to controlsystem 190. In one example, the control system may adjust engine outputand/or the wheel brakes to increase vehicle stability in response tosensor(s) 199.

FIG. 2 shows a schematic depiction of a vehicle system 206. The vehiclesystem 206 includes an engine system 208 coupled to an emissions controlsystem 251 and a fuel system 218. Emission control system 251 includes afuel vapor container or canister 222 which may be used to capture andstore fuel vapors. In some examples, vehicle system 206 may be a hybridelectric vehicle system.

The engine system 208 may include an engine 210 having a plurality ofcylinders 230. The engine 210 includes an engine intake 223 and anengine exhaust 225. The engine intake 223 includes a throttle 262fluidly coupled to the engine intake manifold 244 via an intake passage242. The engine exhaust 225 includes an exhaust manifold 248 leading toan exhaust passage 235 that routes exhaust gas to the atmosphere. Theengine exhaust 225 may include one or more exhaust catalyst 270, whichmay be mounted in a close-coupled position in the exhaust. One or moreemission control devices may include a three-way catalyst, lean NO_(x)trap, diesel particulate filter, oxidation catalyst, etc. It will beappreciated that other components may be included in the engine such asa variety of valves and sensors.

An air intake system hydrocarbon trap (AIS HC) 224 may be placed in theintake manifold of engine 210 to adsorb fuel vapors emanating fromunburned fuel in the intake manifold, puddled fuel from leaky injectorsand/or fuel vapors in crankcase ventilation emissions during engine-offperiods. The AIS HC may include a stack of consecutively layeredpolymeric sheets impregnated with HC vapor adsorption/desorptionmaterial. Alternately, the adsorption/desorption material may be filledin the area between the layers of polymeric sheets. Theadsorption/desorption material may include one or more of carbon,activated carbon, zeolites, or any other HC adsorbing/desorbingmaterials. When the engine is operational causing an intake manifoldvacuum and a resulting airflow across the AIS HC, the trapped vapors arepassively desorbed from the AIS HC and combusted in the engine. Thus,during engine operation, intake fuel vapors are stored and desorbed fromAIS HC 224. In addition, fuel vapors stored during an engine shutdowncan also be desorbed from the AIS HC during engine operation. In thisway, AIS HC 224 may be continually loaded and purged, and the trap mayreduce evaporative emissions from the intake passage even when engine210 is shut down.

Fuel system 218 may include a fuel tank 220 coupled to a fuel pumpsystem 221. The fuel pump system 221 may include one or more pumps forpressurizing fuel delivered to the injectors of engine 210, such as theexample injector 266 shown. While only a single injector 266 is shown,additional injectors are provided for each cylinder. It will beappreciated that fuel system 218 may be a return-less fuel system, areturn fuel system, or various other types of fuel system. Fuel tank 220may hold a plurality of fuel blends, including fuel with a range ofalcohol concentrations, such as various gasoline-ethanol blends,including E10, E85, gasoline, etc., and combinations thereof. A fuellevel sensor 234 located in fuel tank 220 may provide an indication ofthe fuel level (“Fuel Level Input”) to controller 212. As depicted, fuellevel sensor 234 may comprise a float connected to a variable resistor.Alternatively, other types of fuel level sensors may be used.

Vapors generated in fuel system 218 may be routed to an evaporativeemissions control system 251 which includes a fuel vapor canister 222via vapor recovery line 231, before being purged to the engine intake223. Vapor recovery line 231 may be coupled to fuel tank 220 via one ormore conduits and may include one or more valves for isolating the fueltank during certain conditions. For example, vapor recovery line 231 maybe coupled to fuel tank 220 via one or more or a combination of conduits271, 273, and 275.

Further, in some examples, one or more fuel tank vent valves in conduits271, 273, or 275. Among other functions, fuel tank vent valves may allowa fuel vapor canister of the emissions control system to be maintainedat a low pressure or vacuum without increasing the fuel evaporation ratefrom the tank (which would otherwise occur if the fuel tank pressurewere lowered). For example, conduit 271 may include a grade vent valve(GVV) 287, conduit 273 may include a fill limit venting valve (FLVV)285, and conduit 275 may include a grade vent valve (GVV) 283. Such ventvalves may be default-open valves which close responsive to fuel filllevel, for example. In some embodiments, one or more of valves 283, 285,and 287 may be actuatable in order to increase or decrease the rate offuel vapor flow through vapor recovery line 231 responsive to operatingconditions. Further, in some examples, recovery line 231 may be coupledto a fuel filler system 219. In some examples, fuel filler system mayinclude a fuel cap 205 for sealing off the fuel filler system from theatmosphere. Refueling system 219 is coupled to fuel tank 220 via a fuelfiller pipe or neck 211.

Further, refueling system 219 may include refueling lock 245. In someembodiments, refueling lock 245 may be a fuel cap locking mechanism. Thefuel cap locking mechanism may be configured to automatically lock thefuel cap in a closed position so that the fuel cap cannot be opened. Forexample, the fuel cap 205 may remain locked via refueling lock 245 whilepressure or vacuum in the fuel tank is greater than a threshold. Inresponse to a refuel request, e.g., a vehicle operator initiatedrequest, the fuel tank may be depressurized and the fuel cap unlockedafter the pressure or vacuum in the fuel tank falls below a threshold. Afuel cap locking mechanism may be a latch or clutch, which, whenengaged, prevents the removal of the fuel cap. The latch or clutch maybe electrically locked, for example, by a solenoid, or may bemechanically locked, for example, by a pressure diaphragm.

In some embodiments, refueling lock 245 may be a filler pipe valvelocated at a mouth of fuel filler pipe 211. In such embodiments,refueling lock 245 may not prevent the removal of fuel cap 205. Rather,refueling lock 245 may prevent the insertion of a refueling pump intofuel filler pipe 211. The filler pipe valve may be electrically locked,for example by a solenoid, or mechanically locked, for example by apressure diaphragm.

In some embodiments, refueling lock 245 may be a refueling door lock,such as a latch or a clutch which locks a refueling door located in abody panel of the vehicle. The refueling door lock may be electricallylocked, for example by a solenoid, or mechanically locked, for exampleby a pressure diaphragm.

In embodiments where refueling lock 245 is locked using an electricalmechanism, refueling lock 245 may be unlocked by commands fromcontroller 212, for example, when a fuel tank pressure decreases below apressure threshold. In embodiments where refueling lock 245 is lockedusing a mechanical mechanism, refueling lock 245 may be unlocked via apressure gradient, for example, when a fuel tank pressure decreases toatmospheric pressure.

Emissions control system 251 may include one or more emissions controldevices, such as one or more fuel vapor canisters 222 filled with anappropriate adsorbent, the canisters are configured to temporarily trapfuel vapors (including vaporized hydrocarbons) during fuel tankrefilling operations and “running loss” (that is, fuel vaporized duringvehicle operation). In one example, the adsorbent used is activatedcharcoal. Emissions control system 251 may further include a canisterventilation path or vent line 227 which may route gases out of thecanister 222 to the atmosphere when storing, or trapping, fuel vaporsfrom fuel system 218.

Canister 222 may include a buffer 222 a (or buffer region), each of thecanister and the buffer comprising the adsorbent. As shown, the volumeof buffer 222 a may be smaller than (e.g., a fraction of) the volume ofcanister 222. The adsorbent in the buffer 222 a may be same as, ordifferent from, the adsorbent in the canister (e.g., both may includecharcoal). Buffer 222 a may be positioned within canister 222 such thatduring canister loading, fuel tank vapors are first adsorbed within thebuffer, and then when the buffer is saturated, further fuel tank vaporsare adsorbed in the canister. In comparison, during canister purging,fuel vapors are first desorbed from the canister (e.g., to a thresholdamount) before being desorbed from the buffer. In other words, loadingand unloading of the buffer is not linear with the loading and unloadingof the canister. As such, the effect of the canister buffer is to dampenany fuel vapor spikes flowing from the fuel tank to the canister,thereby reducing the possibility of any fuel vapor spikes going to theengine. One or more temperature sensors 232 may be coupled to and/orwithin canister 222. As fuel vapor is adsorbed by the adsorbent in thecanister, heat is generated (heat of adsorption). Likewise, as fuelvapor is desorbed by the adsorbent in the canister, heat is consumed. Inthis way, the adsorption and desorption of fuel vapor by the canistermay be monitored and estimated based on temperature changes within thecanister.

Vent line 227 may also allow fresh air to be drawn into canister 222when purging stored fuel vapors from fuel system 218 to engine intake223 via purge line 228 and purge valve 261. For example, purge valve 261may be normally closed but may be opened during certain conditions sothat vacuum from engine intake manifold 244 is provided to the fuelvapor canister for purging. In some examples, vent line 227 may includean air filter 259 disposed therein upstream of a canister 222. Ahydrocarbon sensor 229 may be deposed within vent line 227 between afresh air port of canister 222 and canister vent valve 297. In this way,hydrocarbon breakthrough from canister 222 may be monitored.

In some examples, the flow of air and vapors between canister 222 andthe atmosphere may be regulated by a canister vent valve coupled withinvent line 227. When included, the canister vent valve may be a normallyopen valve, so that fuel tank isolation valve 252 (FTIV) may controlventing of fuel tank 220 with the atmosphere. FTIV 252 may be positionedbetween the fuel tank and the fuel vapor canister within conduit 278.FTIV 252 may be a normally closed valve, that when opened, allows forthe venting of fuel vapors from fuel tank 220 to canister 222. Fuelvapors may then be vented to atmosphere, or purged to engine intakesystem 223 via canister purge valve 261.

Fuel system 218 may be operated by controller 212 in a plurality ofmodes by selective adjustment of the various valves and solenoids. Forexample, the fuel system may be operated in a fuel vapor storage mode(e.g., during a fuel tank refueling operation and with the engine notrunning), wherein the controller 212 may open isolation valve 252 whileclosing canister purge valve (CPV) 261 to direct refueling vapors intocanister 222 while preventing fuel vapors from being directed into theintake manifold.

As another example, the fuel system may be operated in a refueling mode(e.g., when fuel tank refueling is requested by a vehicle operator),wherein the controller 212 may open isolation valve 252, whilemaintaining canister purge valve 261 closed, to depressurize the fueltank before allowing enabling fuel to be added therein. As such,isolation valve 252 may be kept open during the refueling operation toallow refueling vapors to be stored in the canister. After refueling iscompleted, the isolation valve may be closed.

As yet another example, the fuel system may be operated in a canisterpurging mode (e.g., after an emission control device light-offtemperature has been attained and with the engine running), wherein thecontroller 212 may open canister purge valve 261 while closing isolationvalve 252. Herein, the vacuum generated by the intake manifold of theoperating engine may be used to draw fresh air through vent 27 andthrough fuel vapor canister 22 to purge the stored fuel vapors intointake manifold 44. In this mode, the purged fuel vapors from thecanister are combusted in the engine. The purging may be continued untilthe stored fuel vapor amount in the canister is below a threshold.

Controller 212 may comprise a portion of a control system 214. Controlsystem 214 is shown receiving information from a plurality of sensors216 (various examples of which are described herein) and sending controlsignals to a plurality of actuators 281 (various examples of which aredescribed herein). As one example, sensors 216 may include exhaust gassensor 237 located upstream of the emission control device, temperaturesensor 233, pressure sensor 291, and canister temperature sensor 243.Other sensors such as pressure, temperature, air/fuel ratio, andcomposition sensors may be coupled to various locations in the vehiclesystem 206. As another example, the actuators may include throttle 262,fuel tank isolation valve 253, canister purge valve 261, and canistervent valve 297. The control system 214 may include a controller 212. Thecontroller may receive input data from the various sensors, process theinput data, and trigger the actuators in response to the processed inputdata based on instruction or code programmed therein corresponding toone or more routines. Example control routines are described herein withregard to FIGS. 3 and 5.

In some examples, the controller may be placed in a reduced power modeor sleep mode, wherein the controller maintains essential functionsonly, and operates with a lower battery consumption than in acorresponding awake mode. For example, the controller may be placed in asleep mode following a vehicle-off event in order to perform adiagnostic routine at a duration after the vehicle-off event. Thecontroller may have a wake input that allows the controller to bereturned to an awake mode based on an input received from one or moresensors. For example, the opening of a vehicle door may trigger a returnto an awake mode.

Leak detection routines may be intermittently performed by controller212 on fuel system 218 to confirm that the fuel system is not degraded.As such, leak detection routines may be performed while the engine isoff (engine-off leak test) using engine-off natural vacuum (EONV)generated due to a change in temperature and pressure at the fuel tankfollowing engine shutdown and/or with vacuum supplemented from a vacuumpump. Alternatively, leak detection routines may be performed while theengine is running by operating a vacuum pump and/or using engine intakemanifold vacuum. For example, an evaporative leak check module (notshown) may be coupled within vent line 227.

In some configurations, a canister vent valve (CVV) 297 may be coupledwithin vent line 227. CVV 297 may function to adjust a flow of air andvapors between canister 222 and the atmosphere. The CVV may also be usedfor diagnostic routines. When included, the CVV may be opened duringfuel vapor storing operations (for example, during fuel tank refuelingand while the engine is not running) so that air, stripped of fuel vaporafter having passed through the canister, can be pushed out to theatmosphere. Likewise, during purging operations (for example, duringcanister regeneration and while the engine is running), the CVV may beopened to allow a flow of fresh air to strip the fuel vapors stored inthe canister. In some examples, CVV 297 may be a solenoid valve whereinopening or closing of the valve is performed via actuation of a canistervent solenoid. In particular, the canister vent valve may be an openthat is closed upon actuation of the canister vent solenoid. In someexamples, CVV 297 may be configured as a latchable solenoid valve. Inother words, when the valve is placed in a closed configuration, itlatches closed without requiring additional current or voltage. Forexample, the valve may be closed with a 100 ms pulse, and then opened ata later time point with another 100 ms pulse. In this way, the amount ofbattery power required to maintain the CVV closed is reduced. Inparticular, the CVV may be closed while the vehicle is off, thusmaintaining battery power while maintaining the fuel emissions controlsystem sealed from atmosphere.

As described with regard to FIG. 1, a vehicle may be operated inECO-mode in order to limit running and/or evaporative emissions. Whenrefueling in ECO-mode, limiting the emissions of hydrocarbon vapor maybe prioritized over enabling the fuel fill level to reach a maximum filllevel for the fuel tank. Thus, if a fuel vapor canister becomessaturated with hydrocarbons during the refueling process, the refuelingevent may be ended prior to the fill limit reaching the default maximumfill level. For example, a hot canister has a lower adsorption capacitythan does a cool canister. In hot climates, and/or following a prolongeddriving period, the canister temperature may become increased due toheat rejection from the engine, exhaust, asphalt radiation, etc. Assuch, the canister may be incapable of storing enough fuel vapor toaccommodate a tank filling refueling event without emitting hydrocarbonsinto atmosphere.

A flow chart for an example high-level method 300 for a limitedemissions refueling event is shown in FIG. 3. More specifically, method300 may be utilized to automatically stop a refueling event responsiveto detecting hydrocarbon breakthrough from a fuel vapor canisterregardless of fuel fill level. Method 300 will be described withreference to the systems described herein and shown in FIGS. 1-2, thoughit should be understood that similar methods may be applied to othersystems without departing from the scope of this disclosure. Method 300may be carried out by a controller, such as controller 212 shown in FIG.2, and may be stored at the controller as executable instructions innon-transitory memory.

Method 300 begins at 305 and includes evaluating current operatingconditions. Operating conditions may be estimated, measured, and/orinferred, and may include one or more vehicle conditions, such asvehicle speed, vehicle location, etc., various engine conditions, suchas engine status, engine load, engine speed, A/F ratio, etc., variousfuel system conditions, such as fuel level, fuel type, fuel temperature,etc., various evaporative emissions system conditions, such as fuelvapor canister load, fuel tank pressure, etc., as well as variousambient conditions, such as ambient temperature, humidity, barometricpressure, etc. Continuing at 310, method 300 includes determiningwhether a refueling event has been requested. For example, a refuelingevent request may comprise a vehicle operator depression of a refuelingbutton on a vehicle instrument panel in the vehicle (e.g., refuelingbutton 196), or at a refueling door. In some examples, a refuelingrequest may comprise a refueling operator requesting access to a fuelfiller neck, for example, by attempting to open a refueling door, and/orattempting to remove a gas cap. If a refueling event has not beenrequested, the method 300 proceeds to 315, wherein method 300 includesmaintaining the status of the fuel system, and may further includemaintaining the status of the evaporative emissions system. For example,components such as the FTIV, CVV, CPV, fuel pump, and refueling lock maybe signaled by the controller to maintain their current conformationand/or activity. Method 300 may then end.

If a request for refueling is received, method 300 proceeds to 320. At320, method 300 includes determining whether limited emission refuelingfor the vehicle is activated. For example, as described with regard toFIG. 1, limited emission refueling may be activated when the vehicle isoperating in ECO-mode. ECO-mode may be activated by default, based onthe vehicle's location, local ambient conditions, local alerts, etc.,and/or activated by the vehicle operator. For example, an ECO-modeselector switch (e.g., ECO-mode selector switch 197 depicted in FIG. 1)may be engaged to activate ECO-mode. If limited emission refueling isnot active (car is operating in “normal emissions” mode and/or ECO-modeis overridden by the vehicle operator) method 300 proceeds to 325.

At 325, method 300 includes depressurizing the fuel tank. For example,the controller may open a fuel tank isolation valve (such as FTIV 252)and opening or maintaining open a vent path between the fuel vaporcanister and atmosphere (e.g., open CVV 297 and/or place an ELCMchangeover valve in a venting position), while maintaining a canisterpurge valve (e.g., CPV 261) closed, to depressurize the fuel tank beforeenabling fuel to be added therein. The fuel tank isolation valve may beopened in a manner to depressurize the fuel tank at a predeterminedrate, so as to prevent rapid depressurization which may cause damage tofuel system components (e.g., FLVV and GVV, which may cork shut due torapid depressurization). Depressurizing the fuel tank may include eitherdecreasing a positive fuel tank pressure to atmospheric pressure and/orincreasing a negative fuel tank pressure (fuel tank vacuum) toatmospheric pressure. An absolute value for fuel tank pressure (relativeto atmospheric pressure) may thus be monitored during depressurization.

Continuing at 330, method 300 includes granting access to the fuelfiller neck. A refueling lock, (e.g., refueling lock 245), may bemaintained locked until the fuel tank pressure reaches a thresholdpressure (e.g., atmospheric pressure), and then commanded to unlock,thus allowing access to the fuel filler neck only following fuel tankdepressurization.

Continuing at 335, method 300 includes maintaining an unrestricted ventpathway for the duration of the refueling event. For example, the fueltank isolation valve and canister vent path may be maintained open forthe duration of the refueling event in order to allow refueling vaporsto be flowed to the fuel vapor canister, and to allow gasses stripped ofrefueling vapors to be flowed to atmosphere.

Returning to 320, if limited emission refueling is active, then method300 proceeds to 340. At 340, method 300 includes evaluating fuel systemand evaporative emissions system conditions. Conditions may includecanister load, canister temperature, fuel tank fill level, fuel tankpressure, fuel temperature, fuel composition, fuel RVP, etc. Continuingat 345, method 300 includes determining whether the canister load isbelow a threshold. The canister load threshold may be predetermined orbased on current operating conditions. For example, the canister loadthreshold may represent whether the canister currently has theadsorption capacity to store the fuel vapor currently in the fuel tankalong with an expected amount of fuel vapor generated while fuel isbeing added to the fuel tank. If the canister load is above thethreshold, then method 300 proceeds to 350, and includes maintaining theFTIV closed and maintaining the refueling lock engaged. In other words,if it is determined that refueling is likely to lead to breakthroughemissions prior to the dispensation of a threshold quantity of fuel, therefueling event is prevented from proceeding.

Continuing at 355, method 300 includes indicating to the vehicleoperator that the fuel vapor canister must be purged prior to refueling.For example, a message may be presented to the vehicle operator via ahuman-machine interface (HMI). The message may comprise visible and/oraudible components. In some examples, additional instructions may beprovided to activate the vehicle engine in order to generate intakevacuum which may be used to purge the fuel vapor canister. Additionallyor alternatively, fuel vapor stored within the fuel tank may be purgedto the engine for combustion to increase capacity of the canister toadsorb fuel vapor generated during fuel dispensation. For example, ifthe canister temperature is high and thus the adsorbance capacity of thecanister is low, the canister load threshold indicated at 345 may berelatively low. Thus, reducing the amount of fuel vapor entrained to thefuel vapor canister during fuel tank depressurization may enablerefueling while the vehicle is in ECO-mode. In some scenarios, thevehicle operator may be able to override ECO-mode thus allowing forrefueling under “normal emissions” parameters, wherein threshold forcanister hydrocarbon sensor output is increased or nullified, and/orlimited emissions refueling parameters are designated as inactive.Method 300 may then end.

Returning to 345, if the fuel vapor canister load is below thethreshold, method 300 then proceeds to 360. At 360, method 300 includesdepressurizing the fuel tank, as described at 325. Continuing at 365,method 300 includes granting access to the fuel filler neck, asdescribed at 330. Continuing at 370, method 300 includes monitoring theoutput of the vent hydrocarbon sensor (e.g., hydrocarbon sensor 229) forthe duration of the refueling event. Monitoring the output of the venthydrocarbon sensor may include receiving signals from one or morehydrocarbon sensors continuously, or at predetermined time intervalssuch that a predetermined number of vent hydrocarbon level measurementscan be performed over the duration of the refueling event. Thepredetermined number of measurements and the predetermined timeintervals may be set depending on a noise characteristic of the sensorand/or hydrocarbon level signal, for example. In one example, thepredetermined time interval may be 5 seconds or 10 seconds, or frequentenough to collect a reliable number of measurements representative ofthe levels of hydrocarbon breakthrough typically observed duringrefueling. The end of the refueling event may be indicated based on oneor more of the fuel tank pressure and fuel level. For example, the endof the refueling event may be indicated when a fuel level has plateauedfor a duration, and when a fuel tank pressure has not increased over theplateau duration. In other examples, the end of the refueling event maybe indicated responsive to a refueling nozzle being removed from thefuel filler neck, replacement of a fuel cap, closing of a refuelingdoor, etc.

Continuing at 375, method 300 includes determining whether the output ofthe vent hydrocarbon sensor is greater than a threshold. The thresholdmay be predetermined or based on current operating conditions, and mayrepresent a minimum amount of hydrocarbons in the canister vent linethat can reliably be reported by the hydrocarbon sensor. In other words,the output of the hydrocarbon sensor may be monitored for breakthroughof hydrocarbons from the fuel vapor canister in to the canister ventline. If the vent hydrocarbon sensor output is below the threshold,method 300 proceeds to 380. At 380, method 300 includes maintaining anunrestricted canister vent pathway. For example, the FTIV and CVV may bemaintained open.

If the vent hydrocarbon sensor output increases above the threshold,method 300 proceeds to 385. At 385, method 300 includes restricting thecanister vent pathway. For example, the FTIV and/or CVV may be closed.In some embodiments, an ELCM changeover valve may be placed in arestricting conformation. In some embodiments, one or more fuel tankvent valves, such as an FLVV or GVV, may be commanded closed. Byrestricting the vent pathway, fuel vapor will build up behind therestricting valve, increasing the fuel tank pressure and thus triggeringan automatic shutoff of the fuel dispenser. The technical result ofrestricting the vent pathway responsive to the output of a venthydrocarbon sensor increasing above a threshold is that refuelingemissions are mitigated. In some examples, the fuel system and/orevaporative emissions system may be backfilled with air and/or inertgas. For example, and ELCM pump located in the canister vent pathway maybe activated to pump atmospheric air into the canister vent path. Thismay increase the rate of fuel tank pressure accumulation, hastening theautomatic shutoff event. Further, backfilling may maintain the fuel tankpressure following the automatic shutoff event, decreasing the length oftime before a subsequent automatic shutoff event following an attempt bythe fuel dispenser operator to add additional fuel to (trickle fill) thefuel tank.

When the refueling event is stopped, either by automatic ventrestriction due to fuel fill level, forced vent restriction due tohydrocarbon breakthrough, or refueling operator action, method 300proceeds to 390. At 390, method 300 includes restricting access to thefuel filler neck following termination of the refueling event.Termination of the refueling event may be indicated by the withdrawal ofa refueling nozzle from the fuel filler neck, replacement of a fuel cap,closing of a refueling door, etc. Restricting access to the fuel fillerneck may include actuating the refueling lock. Continuing at 395, method300 includes restoring the fuel system to a default conformation. Forexample, the FTIV may be closed, the CVV may be opened, and the CPV maybe closed or maintained closed. Opening the CVV may be performedresponsive to a vent hydrocarbon sensor output decreasing below athreshold. Continuing at 399, method 300 includes updating fuel systemparameters. For example, the fuel fill level and canister load may beupdated, a canister purge schedule may be updated, etc. Method 300 maythen end.

FIG. 4 shows an example timeline 400 for a refueling event in accordancewith the current disclosure. Timeline 400 includes plot 405, indicatingwhether a refueling event has been requested over time, and plot 410,indicating whether limited emission refueling parameters are active overtime. Timeline 400 further includes plot 415, indicating the status ofan FTIV over time; plot 420, indicating fuel filler neck access statusover time; and plot 425, indicating the status of a CVV over time.Timeline 400 further includes plot 430, indicating fuel tank fill levelover time, and plot 435, indicating an output of an FTPT over time. Line436 represents a fuel tank pressure threshold above which a refuelingnozzle will be triggered to cease dispensing fuel automatically. Line438 represents a fuel tank pressure threshold for granting access to thefuel filler neck following fuel tank depressurization. Timeline 400further includes plot 440, indicating an output of a vent hydrocarbonsensor over time. Line 441 represents a threshold hydrocarbonconcentration for indicating hydrocarbon breakthrough from a fuel vaporcanister.

At time t₀, no refueling event has been requested, as indicated by plot405. As such, the FTIV is closed, as indicated by plot 415, fuel fillerneck access is restricted, as indicated by plot 420, and the CVV isopen, as indicated by plot 425. At time t₁, a refueling request isreceived. Accordingly, the FTIV is opened at time t₂, while the CVV ismaintained open, and fuel filler neck access is maintained restricted.In response to opening the FTIV, the fuel tank pressure decreases, asshown by plot 435. Although fuel vapor is being vented from the fueltank, the output of the vent hydrocarbon sensor does not significantlyincrease, indicating that the fuel vapor canister is adsorbing thevented hydrocarbons, and releasing gasses stripped of hydrocarbons intothe canister vent pathway.

At time t₃, the output of the FTPT decreases to the thresholdrepresented by line 438. Accordingly, fuel filler neck access isgranted, while the FTIV and CVV are maintained in open conformations. Attime t₄, fuel dispensation is initiated. The fuel tank pressureundergoes an initial pressure rise and then decreases to a steady-statepressure that is proportional to the flow rate of fuel dispensed in tothe fuel tank. The fuel tank fill level increases linearly from time t₄until time t₅. At time t₅, the vent hydrocarbon sensor output increasesabove the threshold represented by line 441, indicating hydrocarbonbreakthrough from the canister into the canister vent. As limitedemission refueling is active, as indicated by plot 410, the CVV isclosed in order to prevent further hydrocarbon emission. Closing the CVVblocks the flow of fuel vapor out of the fuel tank, increasing the fueltank pressure above the threshold represented by line 436. The rise infuel tank pressure causes an automatic shut-off signal to be sent to thefuel dispenser. Accordingly, the fuel dispenser is shut off at time t₅.Fuel dispensing ceases and the fuel tank fill level levels off.

From time t₆ to time t₇, the fuel dispenser operator attempts totrickle-fill additional fuel in the fuel tank. Accordingly, fuel tankpressure increases, as shown by plot 435, although a minimal amount offuel is added to the tank, as shown by plot 430. At time t₇, anotherautomatic shut-off event occurs. The fuel level again stops increasing,and the fuel tank pressure decreases slightly. Another trickle-fillingevent followed by an automatic shut-off event occurs from time t₈ totime t₉. Following time t₉, the fuel tank pressure decreases, as shownby plot 435. The refueling event is then finalized. At time t₁₀, fuelfiller neck access is restricted, and the FTIV is closed. Closing theFTIV limits the amount of fuel vapor within the fuel vapor canister andcanister vent line. Additional fuel vapor is adsorbed by the canister,and the hydrocarbon concentration in the canister vent decreases, asindicated by plot 440. At time t₁₁, the vent hydrocarbon sensor outputdecreases below the threshold represented by line 441. Accordingly, theCVV is returned to an open conformation.

While the method described with regard to FIG. 3 limits emissions duringrefueling events, filling a fuel tank following canister breakthroughmay be challenging if the canister vent pathway is restricted in thisway. A flow chart for an example high-level method 500 for a limitedemissions refueling event that does not limit fuel fill level is shownin FIG. 5. More specifically, method 500 may be utilized to divertrefueling vapors into the intake manifold of a vehicle responsive tohydrocarbon breakthrough from a fuel vapor canister. Method 500 will bedescribed with reference to the systems described herein and shown inFIGS. 1-2, though it should be understood that similar methods may beapplied to other systems without departing from the scope of thisdisclosure. Method 500 may be carried out by a controller, such ascontroller 212 shown in FIG. 2, and may be stored at the controller asexecutable instructions in non-transitory memory.

Method 500 begins at 505 and includes evaluating current operatingconditions. Operating conditions may be estimated, measured, and/orinferred, and may include one or more vehicle conditions, such asvehicle speed, vehicle location, etc., various engine conditions, suchas engine status, engine load, engine speed, A/F ratio, etc., variousfuel system conditions, such as fuel level, fuel type, fuel temperature,etc., various evaporative emissions system conditions, such as fuelvapor canister load, fuel tank pressure, etc., as well as variousambient conditions, such as ambient temperature, humidity, barometricpressure, etc. Continuing at 510, method 500 includes determiningwhether a refueling event has been requested. For example, a refuelingevent request may comprise a vehicle operator depression of a refuelingbutton on a vehicle instrument panel in the vehicle (e.g., refuelingbutton 196), or at a refueling door. In some examples, a refuelingrequest may comprise a refueling operator requesting access to a fuelfiller neck, for example, by attempting to open a refueling door, and/orattempting to remove a gas cap. If a refueling event has not beenrequested, the method 500 proceeds to 515, wherein method 500 includesmaintaining the status of the fuel system, and may further includemaintaining the status of the evaporative emissions system. For example,components such as the FTIV, CVV, CPV, fuel pump, and refueling lock maybe signaled by the controller to maintain their current conformationand/or activity. Method 500 may then end.

If a refueling event has been requested, method 500 proceeds to 520. At520, method 500 includes depressurizing the fuel tank. For example, thecontroller may open a fuel tank isolation valve (such as FTIV 252) andopening or maintaining open a vent path between the fuel vapor canisterand atmosphere (e.g., open CVV 297 and/or place an ELCM changeover valvein a venting position), while maintaining a canister purge valve (e.g.,CPV 261) closed, to depressurize the fuel tank before enabling fuel tobe added therein. The fuel tank isolation valve may be opened in amanner to depressurize the fuel tank at a predetermined rate, so as toprevent rapid depressurization which may cause damage to fuel systemcomponents (e.g., FLVV and GVV, which may cork shut due to rapiddepressurization). Depressurizing the fuel tank may include eitherdecreasing a positive fuel tank pressure to atmospheric pressure and/orincreasing a negative fuel tank pressure (fuel tank vacuum) toatmospheric pressure. An absolute value for fuel tank pressure (relativeto atmospheric pressure) may thus be monitored during depressurization.

Continuing at 525, method 500 includes granting access to the fuelfiller neck. A refueling lock, (e.g., refueling lock 245), may bemaintained locked until the fuel tank pressure reaches a thresholdpressure (e.g., atmospheric pressure), and then commanded to unlock,thus allowing access to the fuel filler neck only following fuel tankdepressurization.

Continuing at 530, method 500 includes determining whether limitedemission refueling for the vehicle is activated. For example, asdescribed with regard to FIG. 1, limited emission refueling may beactivated when the vehicle is operating in ECO-mode. ECO-mode may beactivated by default, based on the vehicle's location, local ambientconditions, local alerts, etc., and/or activated by the vehicleoperator. For example, an ECO-mode selector switch (e.g., ECO-modeselector switch 197 depicted in FIG. 1) may be engaged to activateECO-mode. If limited emission refueling is not active (car is operatingin “normal emissions” mode and/or ECO-mode is overridden by the vehicleoperator, method 500 proceeds to 535.

At 535, method 500 includes maintaining the flow of refueling gassesthrough the canister vent pathway for the duration of the refuelingevent. As fuel is added to the fuel tank, refueling vapors aregenerated. The refueling vapors are ported to the fuel vapor canister,where hydrocarbons are adsorbed there within. Gasses stripped of fuelvapor may then exit the fuel vapor canister. Maintaining the flow ofrefueling gasses through the canister vent pathway may includemaintaining an FTIV (or VBV) open, maintaining a CPV closed, andmaintaining a CVV open or otherwise maintaining a coupling the vent portof the canister to atmosphere. At the end of the refueling event, theFTIV may be closed and the CVV and CPV may be operated under defaultlogic.

When the refueling event is stopped, either by automatic ventrestriction due to fuel fill level, refueling operator action or byother means, method 500 then proceeds to 540. At 540, method 500includes restricting access to the fuel filler neck followingtermination of the refueling event. Termination of the refueling eventmay be indicated by the withdrawal of a refueling nozzle from the fuelfiller neck, replacement of a fuel cap, closing of a refueling door,etc. Restricting access to the fuel filler neck may include actuatingthe refueling lock. Continuing at 545, method 500 includes restoring thefuel system to a default conformation. For example, the FTIV may beclosed, the CVV may be opened, and the CPV may be closed or maintainedclosed. Opening the CVV may be performed responsive to a venthydrocarbon sensor output decreasing below a threshold. Continuing at550, method 500 includes updating fuel system parameters. For example,the fuel fill level and canister load may be updated, a canister purgeschedule may be updated, etc. Method 500 may then end.

Returning to 530, if limited emission refueling is active, then method500 proceeds to 555. At 555, method 500 includes monitoring the outputof the vent hydrocarbon sensor (e.g., hydrocarbon sensor 229) for theduration of the refueling event. Monitoring the output of the venthydrocarbon sensor may include receiving signals from one or morehydrocarbon sensors continuously or at predetermined time intervals suchthat a predetermined number of vent hydrocarbon level measurements canbe performed over the duration of the refueling event. The predeterminednumber of measurements and the predetermined time intervals may be setdepending on a noise characteristic of the sensor and/or hydrocarbonlevel signal, for example. In one example, the predetermined timeinterval may be 5 seconds or 10 seconds, or frequent enough to collect areliable number of measurements representative of the levels ofhydrocarbon breakthrough typically observed during refueling. The end ofthe refueling event may be indicated based on one or more of the fueltank pressure and fuel level. For example, the end of the refuelingevent may be indicated when a fuel level has plateaued for a duration,and when a fuel tank pressure has not increased over the plateauduration. In other examples, the end of the refueling event may beindicated responsive to a refueling nozzle being removed from the fuelfiller neck, replacement of a fuel cap, closing of a refueling door,etc.

Continuing at 560, method 500 includes determining whether the output ofthe vent hydrocarbon sensor is greater than a threshold. The thresholdmay be predetermined or based on current operating conditions, and mayrepresent a minimum amount of hydrocarbons in the canister vent linethat can reliably be reported by the hydrocarbon sensor. In other words,the output of the hydrocarbon sensor may be monitored for breakthroughof hydrocarbons from the fuel vapor canister in to the canister ventline. If the vent hydrocarbon sensor output is below the threshold,method 500 proceeds to 565. At 565, method 500 includes flowing gassesstripped of fuel vapor through the canister vent pathway. For example,the FTIV and CVV may be maintained open, while the CPV is maintainedclosed. Method 500 may then proceed to 540, and include restrictingaccess to the fuel filler neck following the termination of therefueling event as described above.

Returning to 560, if the vent hydrocarbon sensor output increases abovethe threshold, then method 500 proceeds to 570. At 570, method 500includes flowing refueling vapors into the vehicle intake manifold. Asan example, the CPV may be opened, while the CVV may be duty cycled sothat the path through the canister purge port is less restrictive thanthe path through the canister vent port. In this way, fuel vapor that isnot bound to the canister adsorbent is directed to the intake manifold,rather than to atmosphere. Unlike the method described with regard toFIG. 3, the redirection of the fuel vapor does not automatically buildpressure that would result in the cessation of fuel dispensation, thusallowing for the fuel tank to be filled. In some examples, the intakethrottle may be closed or maintained closed. Further, in some examples,the intake and/or exhaust valves of one or more engine cylinders may beclosed or maintained closed.

Continuing at 575, method 500 includes restricting access to the fuelfiller neck following termination of the refueling event. Termination ofthe refueling event may be indicated by the withdrawal of a refuelingnozzle from the fuel filler neck, replacement of a fuel cap, closing ofa refueling door, etc. Restricting access to the fuel filler neck mayinclude actuating the refueling lock.

Continuing at 580, method 500 includes isolating unbound fuel vapors.This may include closing an FTIV to isolate fuel vapor in the fuel tank,may further include closing a CPV to isolate fuel vapor within theintake manifold, and may further include closing a CVV to isolate fuelvapor within the canister vent pathway. Continuing at 585, method 500includes updating fuel system parameters. For example, the fuel filllevel and canister load may be updated, a canister purge schedule may beupdated, etc. Continuing at 590, method 500 includes updating enginestartup parameters. For example, engine fueling controls and A/F ratiosmay be adjusted to reduce the quantity of fuel injected at enginestartup based on the amount of fuel vapor within the engine intakesystem. For hybrid vehicles, start-stop vehicles, and other vehiclesthat may not startup an engine at key-on, the parameters governingengine startup may be adjusted in order to prevent operating the vehiclewith fuel vapor trapped in the intake. For example, engine startup maybe earlier and/or with reduced thresholds as compared to key-on eventswhere the intake manifold is not holding fuel vapor. Method 500 may thenend.

In some examples, a refueling method may comprise elements of bothmethod 300 and method 500. For example, if a fuel fill level is above athreshold, hydrocarbon emissions may be limited by restricting acanister vent pathway, while hydrocarbon emissions may be limited bydiverting refueling vapors to the engine intake if a fuel fill level isbelow the threshold. Similar logic may be applied based on batterycharge, distance to next fueling station on a programmed trip, etc. Insome examples, a canister vent pathway may initially be restricted basedon hydrocarbon breakthrough, then refueling vapors may be diverted tothe engine intake following a threshold number of trickle-fill attempts.In this way, emissions may be restricted while allowing for increasedfuel fill level in some scenarios.

FIG. 6 shows an example timeline 600 for a refueling event in accordancewith the current disclosure. Timeline 600 includes plot 605, indicatingwhether a refueling event has been requested over time, and plot 610,indicating whether limited emission refueling parameters are active overtime. Timeline 600 further includes plot 615, indicating the status ofan FTIV over time; plot 620, indicating fuel filler neck access statusover time; and plot 625, indicating the status of a CVV over time.Timeline 400 further includes plot 630, indicating the status of a CPVover time, plot 635, indicating fuel tank fill level over time, and plot640, indicating an output of an FTPT over time. Line 642 represents afuel tank pressure threshold above which a refueling nozzle will betriggered to cease dispensing fuel automatically. Line 644 represents afuel tank pressure threshold for granting access to the fuel filler neckfollowing fuel tank depressurization. Timeline 600 further includes plot645, indicating an output of a vent hydrocarbon sensor over time. Line647 represents a threshold hydrocarbon concentration for indicatinghydrocarbon breakthrough from a fuel vapor canister.

At time t₀, no refueling event has been requested, as indicated by plot605. As such, the FTIV is closed, as indicated by plot 615, fuel fillerneck access is restricted, as indicated by plot 620, the CVV is open, asindicated by plot 625, and the CPV is closed, as indicated by plot 630.At time t₁, a refueling request is received. Accordingly, the FTIV isopened at time t₂, while the CVV is maintained open, the CPV ismaintained closed, and fuel filler neck access is maintained restricted.In response to opening the FTIV, the fuel tank pressure decreases, asshown by plot 640. Although fuel vapor is being vented from the fueltank, the output of the vent hydrocarbon sensor does not significantlyincrease, indicating that the fuel vapor canister is adsorbing thevented hydrocarbons, and releasing gasses stripped of hydrocarbons intothe canister vent pathway.

At time t₃, the output of the FTPT decreases to the thresholdrepresented by line 644. Accordingly, fuel filler neck access isgranted, while the FTIV and CVV are maintained in open conformations,and the CPV is maintained in a closed conformation. At time t₄, fueldispensation is initiated. The fuel tank pressure undergoes an initialpressure rise and then decreases to a steady-state pressure that isproportional to the flow rate of fuel dispensed in to the fuel tank. Attime t₅, the vent hydrocarbon sensor output increases above thethreshold represented by line 647, indicating hydrocarbon breakthroughfrom the canister into the canister vent. As limited emission refuelingis active, as indicated by plot 610, the CPV is opened, and the CVV isduty-cycled between and open and closed position. Accordingly, the fueltank fill level continues to rise linearly, and the fuel tank pressureis maintained relatively constant.

At time t₆, the fuel tank fill level reaches a full fill level, and thefuel tank pressure increases above the threshold represented by line642. The rise in fuel tank pressure causes an automatic shut-off signalto be sent to the fuel dispenser. Accordingly, the fuel dispenser isshut off at time t₆. Fuel dispensing ceases and the fuel tank fill levellevels off. At time t₇, the FTIV is closed, the CPV is closed, the CVVis maintained in an open conformation, and fuel filler neck access isrestricted.

The systems described herein and with reference to FIGS. 1 and 2, alongwith the methods described herein and with reference to FIGS. 3 and 5may enable one or more systems and one or more methods. In one example,a method is presented, comprising: during a first condition, includingan ongoing refueling event, receiving an indication of hydrocarbonbreakthrough from a fuel vapor canister; and flowing refueling vaporsinto an intake manifold responsive to the indication of hydrocarbonbreakthrough. The technical result of implementing this method is thatrefueling emissions stemming from canister breakthrough can bemitigated, while allowing the continuation of the refueling event. Suchan example method may additionally or alternatively comprise updatingone or more engine startup parameters following termination of therefueling event. In any of the preceding example methods, the one ormore fuel system parameters may additionally or alternatively comprise afuel injection quantity. In any of the preceding example methods,flowing refueling vapors into an intake manifold may additionally oralternatively comprise opening a canister purge valve coupled between afuel vapor canister and the intake manifold. In any of the precedingexample methods, flowing refueling vapors into an intake manifoldfurther may additionally or alternatively comprise duty-cycling acanister vent valve coupled between the fuel vapor canister andatmosphere. In any of the preceding example methods, the method mayadditionally or alternatively comprise isolating unbound fuel vaporsfollowing termination of the refueling event. In any of the precedingexample methods, isolating unbound fuel vapors may additionally oralternatively comprise closing the canister purge valve. In any of thepreceding example methods, the indication of hydrocarbon breakthroughfrom the fuel vapor canister may additionally or alternatively comprisean output of a hydrocarbon sensor coupled within the fuel vapor canistervent pathway increasing above a threshold. In any of the precedingexample methods, the method may additionally or alternatively comprisereceiving a request for a refueling event; opening a fuel tank isolationvalve coupled between a fuel and a fuel vapor canister; and removingaccess restrictions to a fuel filler neck responsive to an absolute fueltank pressure decreasing below a threshold. In any of the precedingexample methods, the first condition may additionally or alternativelycomprise active limited emission refueling parameters. In any of thepreceding example methods, limited emission refueling parameters mayadditionally or alternatively be activated in response to a localregulation for the jurisdiction in which the refueling event takesplace. In any of the preceding example methods, the method mayadditionally or alternatively comprise during a second condition,including an active refueling event, restricting flow of refuelingvapors into the intake manifold regardless of an indication ofhydrocarbon breakthrough, including even when the indication ofbreakthrough is generated. In any of the preceding example methods, thelimited emission refueling parameters may additionally or alternativelybe inactive during the second condition.

In another example, a fuel system for a vehicle is presented,comprising: a fuel vapor canister vent pathway comprising a load conduitcoupled to a fuel tank and a vent conduit coupled to atmosphere; one ormore valves coupled within the fuel vapor canister vent pathway; a fuelvapor canister purge pathway comprising a purge conduit coupled betweena fuel vapor canister and an engine intake; a canister purge valvecoupled within the fuel vapor canister purge pathway; a hydrocarbonsensor coupled within the vent conduit; a purge conduit coupled betweenthe fuel vapor canister; a human machine interface configured to receivea refueling request from a vehicle operator and further configured toreceive input from the vehicle operator indicating whether limitedemissions refueling parameters are active; and a controller configuredwith instructions stored in non-transitory memory, that when executed,cause the controller to: depressurize the fuel tank via the fuel vaporcanister vent pathway responsive to an indication that a refuelingrequest has been received by the human machine interface; responsive toan indication that limited emissions refueling parameters are active,monitor an output of the hydrocarbon sensor during a refueling event;and flow refueling vapors into the intake manifold via the fuel vaporcanister purge conduit responsive to the output of the hydrocarbonsensor increasing above a threshold. The technical effect ofimplementing this system is a reduction in ground ozone during refuelingevents. In such an example fuel system the one or more valves coupledwithin the fuel vapor canister vent pathway may additionally oralternatively include a canister vent valve coupled between the fuelvapor canister and atmosphere, and wherein flow refueling vapors intothe intake manifold via the fuel vapor canister purge conduit comprisesopening the canister purge valve and duty-cycling the canister ventvalve. In any of the preceding example fuel systems, the controller mayadditionally or alternatively be further configured with instructionsstored in non-transitory memory, that when executed, cause thecontroller to: flow refueling vapors through the fuel vapor canistervent pathway based on an output of the hydrocarbon sensor below thethreshold.

In yet another example, a method for an evaporative emissions system ispresented, comprising: receiving a request for a refueling event;receiving an indication that limited emissions refueling parameters areactive; venting a fuel tank to atmosphere via a fuel vapor canister;allowing access to a fuel filler neck responsive to an absolute fueltank pressure decreasing below a threshold; monitoring an output of ahydrocarbon sensor coupled between the fuel vapor canister andatmosphere; and during a first condition, responsive to the output ofthe hydrocarbon sensor increasing above a threshold, reducing theresistance of vapor flow through a fuel vapor canister purge pathwayrelative to the resistance of vapor flow through a fuel vapor canistervent pathway. The technical effect of implementing this method is anincrease in the amount of fuel vapor that can be handled by anevaporative emissions system during a refueling event. Such an examplemethod may additionally or alternatively comprise during a secondcondition, responsive to the output of the hydrocarbon sensor increasingabove a threshold, restricting vapor flow through both the fuel vaporcanister purge pathway and the fuel vapor canister vent pathway. In anyof the preceding example methods, the first condition may additionallyor alternatively comprise a fuel tank fill level below a threshold, andthe second condition may additionally or alternatively comprise a fueltank fill level above the threshold. In any of the preceding examplemethods, the first condition may additionally or alternatively followthe second condition, and the first condition may additionally oralternatively follow a number of trickle-fill attempts greater than athreshold.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A method for a vehicle, comprising: duringa first condition, including an ongoing refueling event where a fuelfiller neck is accessible, receiving an indication of hydrocarbonbreakthrough from a fuel vapor canister; and flowing refueling vaporsinto an intake manifold and maintaining access to the fuel filler neckresponsive to the indication of hydrocarbon breakthrough, the refuelingvapors trapped in the intake manifold until an engine start-up.
 2. Themethod of claim 1, further comprising: updating one or more enginestart-up parameters following termination of the refueling event basedon the refueling vapors trapped in the intake manifold.
 3. The method ofclaim 2, wherein the one or more engine start-up parameters comprise afuel injection quantity at the engine start-up.
 4. The method of claim1, wherein flowing refueling vapors into the intake manifold comprisesopening a canister purge valve coupled between the fuel vapor canisterand the intake manifold.
 5. The method of claim 4, wherein flowingrefueling vapors into the intake manifold further comprises duty-cyclinga canister vent valve coupled between the fuel vapor canister andatmosphere.
 6. The method of claim 4, further comprising isolatingunbound fuel vapors following termination of the refueling event.
 7. Themethod of claim 6, wherein isolating unbound fuel vapors comprisesclosing the canister purge valve.
 8. The method of claim 1, wherein theindication of hydrocarbon breakthrough from the fuel vapor canistercomprises an output of a hydrocarbon sensor coupled within a fuel vaporcanister vent pathway, between a fresh air port and a canister ventvalve, increasing above a threshold.
 9. The method of claim 1, furthercomprising: receiving a request for a refueling event; responsive to therequest, depressurizing a fuel tank by opening a fuel tank isolationvalve coupled between a fuel and the fuel vapor canister whilemaintaining access restrictions to the fuel filler neck; and grantingaccess to the fuel filler neck responsive to an absolute fuel tankpressure decreasing below a threshold.
 10. The method of claim 9,wherein the first condition comprises limited emission refuelingparameters being activated.
 11. The method of claim 10, furthercomprising: during a second condition, including an active refuelingevent, restricting flow of refueling vapors into the intake manifoldregardless of the indication of hydrocarbon breakthrough, including evenwhen the indication of hydrocarbon breakthrough is generated.
 12. Themethod of claim 11, wherein the limited emission refueling parametersare inactive during the second condition.
 13. A fuel system for avehicle, comprising: a fuel vapor canister vent pathway comprising aload conduit coupled to a fuel tank and a vent conduit coupled toatmosphere; one or more valves coupled within the fuel vapor canistervent pathway; a fuel vapor canister purge pathway comprising a purgeconduit coupled between a fuel vapor canister and an engine intakemanifold; a canister purge valve coupled within the fuel vapor canisterpurge pathway; a hydrocarbon sensor coupled within the vent conduit; aninterface configured to receive a refueling request from a vehicleoperator and further configured to receive input from the vehicleoperator indicating whether limited emission refueling parameters areactive; and a controller configured with instructions stored innon-transitory memory that, when executed, cause the controller to:depressurize the fuel tank via the fuel vapor canister vent pathwayresponsive to an indication that the refueling request has been receivedby the interface; responsive to an indication that limited emissionrefueling parameters are active, monitor an output of the hydrocarbonsensor during a refueling event in which a fuel filler neck isaccessible; and flow refueling vapors into the engine intake manifoldvia the purge conduit responsive to the output of the hydrocarbon sensorincreasing above a threshold while maintaining access to the fuel fillerneck, the refueling vapors trapped in the engine intake manifold untilan engine start-up following the refueling event.
 14. The fuel system ofclaim 13, wherein the hydrocarbon sensor is coupled within the ventconduit between a fresh air port and a canister vent valve, wherein theone or more valves coupled within the fuel vapor canister vent pathwayincludes the canister vent valve coupled between the fuel vapor canisterand atmosphere, and wherein flowing refueling vapors into the engineintake manifold via the purge conduit comprises opening the canisterpurge valve and duty-cycling the canister vent valve.
 15. The fuelsystem of claim 13, where the controller is further configured withinstructions stored in non-transitory memory that, when executed, causethe controller to: flow the refueling vapors through the fuel vaporcanister vent pathway based on the output of the hydrocarbon sensorbelow the threshold.
 16. A method for an evaporative emissions system,comprising: receiving a request for a refueling event; receiving anindication that limited emission refueling parameters are active;venting a fuel tank to atmosphere via a fuel vapor canister; allowingaccess to a fuel filler neck responsive to an absolute fuel tankpressure decreasing below a threshold; monitoring an output of ahydrocarbon sensor coupled between the fuel vapor canister andatmosphere; and during a first condition where the refueling event isongoing, responsive to the output of the hydrocarbon sensor increasingabove a threshold, maintaining access to the fuel filler neck andreducing a resistance of vapor flow through a fuel vapor canister purgepathway relative to a resistance of vapor flow through a fuel vaporcanister vent pathway to trap refueling vapors in an engine intakemanifold until an engine start-up.
 17. The method of claim 16, furthercomprising: during a second condition, responsive to the output of thehydrocarbon sensor increasing above the threshold, restricting vaporflow through both the fuel vapor canister purge pathway and the fuelvapor canister vent pathway.
 18. The method of claim 17, wherein thefirst condition comprises a fuel tank fill level below a threshold, andthe second condition comprises the fuel tank fill level above thethreshold.
 19. The method of claim 17, wherein the first conditionfollows the second condition, and wherein the first condition furtherfollows a number of trickle-fill attempts greater than a threshold.